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Defender of the Crown *still* crashes in Tandy mode (0.62)

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First post, by trebor

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In an earlier post concerning Defender of the Crown, 'Fizzban' did some debugging and related the following:

"Starting at 8000:9573, the game is copying data byte for byte to 8000:0000 (probably some unpacking). It keeps the target position of the next byte to write as FAR pointer at 8000:0126.

Unfortunatly, that pointer is eventually overwritten and then points to the middle of the interrupt vector. So the remaining copying is completly messing up most of the vectors. As soon as the game try to call the next interrupt (int 0x81 to be precise), it ends in a non-code area and crashes.

No idea so far why this is happening though.."

Here's the basic summary (Non-Technical):
The crashing does not occur if the *.conf file is left at the default 'machine=vga'. The game plays in 'EGA mode'. You play through the whole game without a problem with PC Speaker sound.

When setting 'machine=tandy', places the game in 'Tandy Mode' which enables the Tandy 3-chip sound. However, the came crashes right after the message: "Insert Reel 2 - Press Any Key to Continue".

See prior post and further details here:
Defender of the Crown - EGA version

Any insights or thoughts on what can fix this?

Thanks,
Trebor

Reply 2 of 23, by trebor

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Please, can you explain what is loadfix? What do I need to do? I would love to get Defender of the Crown running with Tandy sound.

Yes, you are right there is a similar issue with Three Stooges. Again, please elaborate on what needs to be done using 'loadfix'.

Thanks In Advance,
Trebor

Reply 3 of 23, by trebor

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For The 3 Stooges I tried:

C:\3STOOGES>loadfix stooges.exe

Results in 3 Stooges playing without any sound.

For Defender of the Crown:

C:\DEFCRWN>loadfix defender.com
I receive the following:

64 kb allocated
Sorry, the DOS memory required by this game is not free.64 kb freed.

Anything I'm doing wrong?

Thanks again,
Trebor

Reply 6 of 23, by trebor

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Here are the "interesting" results with different values for loadfix on defender of the crown:

No Loadfix command used going all the way up to loadfix -43 results in my original post - Crashes with Illegal Opcodes after 'Insert Reel 2'

Loadfix -44 thru Loadfix -56 results in the Game freezing/crashes right at the beginning - After "Press Any Key to Run In Tandy Mode". It seems the game should continue to follow suit with Crashing with Illegal Opcode after 'Insert Reel 2'. My only theory (And I *am* writing out of complete ignorance of the matter is 44kb thru 56 kb is where graphic memory allocation is performed). Someone more knowledgable could perhaps shed more light?

Loadfix -57 thru Loadfix -60 results in my original post - Crashes with the Illegal Opcode message after 'Insert Reel 2'.

Loadfix -61 and above results in "Sorry, the DOS memory required by the game is not free".

Interesting indeed, I thought for the results for -57 thru -60. Don't know if there's any significance to it.

Any other suggestions or ideas?

Thanks again for all and any replies - I really will love to play one (If not the) favorite PC game of all time for me - With Tandy sound 😀

-Trebor

Reply 7 of 23, by wd

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I suppose that version is not the original, but rather a
hacked version (image file with a kind of booter emulation).
And the protection has only been removed from the non-tandy
version.
In the debugger (break in at those intro screens, as the
game seems to be crypted), set a bp at 8000:04a0 and type
"sr ip 4b3" to skip the protection.
Afaict it works fine then.

wd

Reply 8 of 23, by trebor

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Thank you for the information wd, I really appreciate the response. However, I do not know how to perform the tasks you are describing to do. If at all possible, can you kindly provide exact details as to what I need to do?

Can I apply a fix to the game permanently? What you're stating makes sense, as I recall the game came with two 5 1/4" Low Density disk and one 3 1/2" Low Density floppies. I gave the 3 1/2" Low Density Floppy away years ago to a friend- When I first purchased the game (My XT only had duel 5 1/4" Low Density drives). Somewhere in my storage closet, I still have the original box and 5 1/4" floppies. Unfortunately. I don't believe I still have any of the original inserts (Manuel, Quick Reference Card, and I believe a letter from the creator). Sadly, I lost those a while back as well.

Thank You,
Trebor

Reply 9 of 23, by wd

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> If at all possible, can you kindly provide exact details as to what I need to do?

First you have to get dosbox with the debugger enabled,
means you have to compile it yourself. Maybe somewhere
there's a precompiled version floating around.
Then you run the game as usual, and when the introductory
screens appear, you press the pause-key (entering the
debugger). There you type "c 8000:04a0", highlight that
line, press F9 (breakpoint), then F5 (run), and when it
breaks back into the debugger, enter "sr ip 4b3".

> Can I apply a fix to the game permanently?

I tried to do that, but parts of the image (game.dat)
are encrypted, makes binary patching impossible.
In the attached file i modified the loader to apply
a memory patch.
I don't know if the tandy version is intact, as it
obviously wasn't tested, but for me it did work.

Good luck 😀

wd

Attachments

  • Filename
    Defender_com.zip
    File size
    750 Bytes
    Downloads
    257 downloads
    File license
    Fair use/fair dealing exception

Reply 10 of 23, by trebor

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I really truly appreciate all the work and support you have given me in trying to get Defender of the Crown to run in Tandy mode. I'm happy to say with your modified Loader the game progresses further than it ever did. Unfortunately, trying to Raid a Castle results in the game freezing after it gives the 'introduction paragraph' to raiding a castle.

Again, I know there is a 3 1/2" floppy of this game (Which was autoboot). Hopefully, one day someone will dump a "good" complete image of Defender of the Crown. I worked closely with the Producers and Game Designers for both the remastered Defender of the Crown and The 3 Stooges (I was a beta tester and helped in providing input to how the games should play). I was and still am a huge fan of the classic Cinemaware games, as well as enjoying the re-makes. On a positive note, I am very pleased to see The Three Stooges, Sinbad, and It Came From The Desert finally playable in this new DOSBox release 0.62. I was not able to get any of those games to run the way I wanted in any previous versions of DOSBox.

Sadly, not even the "new" Cinemaware has any of the original source code for the original PC/Tandy version of Defender of the Crown - Neither a "retail-full" version. In fact, the version posted at their site is the same copy you can find at Home of the Underdogs or any so-called 'Abandonware' sites.

Maybe some kind soul, like yourself, will come across this thread and be able to assist further.

Thanks again for all your hard work and kindness. I am *extremely* grateful.

-Trebor

Reply 13 of 23, by Crazy Kong

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Isn't it posible to install the files from the original disks to a folder on the harddrive and start the game from this folder.

I got the original 5 1/4 disks of the three stooges and this was possible because there was no copy protection on the disks back in 1991. In the manual it was recomended to install to hard disk.

Reply 19 of 23, by trebor

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Thanks again, el_PuSHeR!

Well, that solved it. Game plays perfect in Tandy mode now - No crashes - No freezing up. It's a shame the version that is widely available is hacked in a way which leaves the Tandy version crippled. As the 3-voice sound is a *big* improvement over the PC Speaker.

While graphically the game looks better on the Amiga - IMHO, the PC/Tandy version has the best gameplay - and *that* is what counts 😀

Hmmm...now only if they restore the colors back in Thexder (Again in Tandy mode) to the way it should be (As seen in v0.61), DOSBox would be perfect (Well, almost) 😉

I just hope more people don't run into the same headache I did with this!

Best Regards,
Trebor